Back contact solar cell assemblies

ABSTRACT

A back contact solar cell assembly and methods for its manufacture and assembly onto a panel for use in space vehicles are described. The solar cell assembly includes a compound semiconductor multijunction solar cell having a contact at the top surface of the solar cell, a conductive semiconductor element extending from the contact on the top surface to the back surface of the assembly where it forms a first back contact of a first polarity type, and a second back contact of a second polarity at the back surface of the assembly electrically coupled to the back surface of the solar cell.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 14/485,378, filed Sep. 12, 2014, which in turn is acontinuation-in-part of U.S. patent application Ser. No. 13/604,833,filed Sep. 6, 2012, which in turn is a continuation-in-part of U.S.patent application Ser. No. 12/637,241, filed Dec. 14, 2009, which inturn is a continuation-in-part of U.S. patent application Ser. No.11/616,596, filed Dec. 27, 2006, and Ser. No. 12/544,001, filed Aug. 19,2009.

This application is also a continuation-in-part of U.S. patentapplication Ser. No. 15/372,086, filed Dec. 7, 2016.

This application is related to U.S. patent application Ser. No.14/729,422, filed Jun. 3, 2015.

This application is also related to U.S. patent application Ser. No.15/439,405, filed Feb. 22, 2017, which is a continuation-in-part of U.S.application Ser. No. 14/334,878, filed Jul. 18, 2014.

This application is related to co-pending U.S. patent application Ser.No. 15/170,269 filed Jun. 1, 2016.

This application is also related to co-pending U.S. patent applicationSer. No. 15/241,418 filed Aug. 19, 2016.

All of the above related applications are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to the field of solar cell arrays and inparticular to back contact solar cells and arrays of such solar cellsfor space/aviation applications and methods for their fabrication.

2. Description of the Related Art

Conventional space solar array panels at present are most oftencomprised of a relatively densely packed arrangement of solar cellsgenerally the size of the semiconductor wafer (typically 100 or 150 mmin diameter) mounted on a rigid supporting panel. A conventional spacesolar array panel may include a panel or support, solar cell assembliesdisposed on the support, interconnection components for connecting thesolar cell assemblies, bypass diodes and blocking diodes also connectedto the solar cells, and electrical terminals for attachment of a cableor harness to transfer the power to a power management distributionsystem and the spacecraft power bus.

Individual solar cells, frequently with a rectangular or generallysquare-shape and sometimes with cropped corners, are connected in seriesto form a string of solar cells, whereby the number of solar cells usedin the string determines the output voltage. Solar cells or strings ofsolar cells can also be interconnected in parallel, so as to increasethe output current. Individual solar cells are provided withinterconnects and a cover glass so as to form so-called CICs(Cell-Interconnect-Cover Glass) assemblies, which are then electricallyinterconnected to form an array. Conventionally, these large solar cellshave been mounted on a support and interconnected using a substantialamount of manual labor. For example, first individual CICs are producedwith each interconnect individually welded to each cell, and each coverglass individually mounted. Then, these CICs are connected in series toform strings, generally in a substantially manual manner, includingwelding or soldering steps. Then, these strings are mounted and securedto a panel or substrate and further electrically interconnected, in aprocess that includes the application of adhesive, wiring, and otherassembly steps.

Close packing of the large solar cells on the space solar array panel ischallenging due to the spatial layout necessary to accommodate discretemetal interconnect elements between the solar cells to form a seriescircuit of interconnected solar cells and to implement and interconnectthe bypass diodes. An additional challenge can sometimes reside in theneed to interconnect a plurality of strings of series connected solarcells in parallel. All of this has traditionally been carried out in amanual and substantially labor-intensive manner.

Accordingly, the present disclosure provides improved array designs andmethods of manufacturing and assembling photovoltaic solar arrays in anautomated manner that can result in decreases in cost, less weight,greater compactness, and increases in performance.

SUMMARY OF THE DISCLOSURE 1. Objects of the Disclosure

It is an object of the present disclosure to provide a solar cell arraywith a high packing density for unifacial solar cells, i.e. cells withanode and cathode contacts on the same surface of the cell.

It is another object of the present disclosure to provide a solar cellarray utilizing solar cell with all backside contacts.

It is still an object of the present disclosure to provide a highpacking density solar cell array with integral interconnections betweensolar cells implemented on the supporting substrate or panel, with thesolar cell assembly having all backside contacts.

It is an object of the present disclosure to provide an improved solarcell assembly or CIC with a cover glass on the top surface and bothanode and cathode electrode contacts on the back surface of the solarcell assembly.

It is also another object of the present disclosure to provide anautomated method for assembling a solar cell array from a CIC in whichthe solar cell assembly has all backside contacts.

It is also another object of the present disclosure to provide anautomated method for assembling a solar cell assembly or CIC with astand-off component disposed in one or more cropped corners of the solarcell.

It is another object of the present disclosure to provide a lightweightsolar cell assembly with unifacial back contacts that is suitable forautomated manufacturing processes.

It is another object of the present disclosure to provide a lightweightdiscrete conductive semiconductor element suitable for automatedprocesses for use in electrical coupling of subcomponents in aphotovoltaic solar cell or array.

It is another object of the disclosure to provide a solar cell arrayplatform or support with high W/kg and W/m² and low cost by utilizingdiscrete conductive traces on the support and lightweight semiconductorconductive elements to make electrical contact with different surfaceportions of the solar cell.

It is another object of the disclosure to provide a solar cell assemblyor module that utilizes an array of wafer-sized solar cells, forexample, solar cells each having a surface area of greater than 50 cm²,and are substantially square in shape, in which the four corners arecropped and accommodate electrical interconnect elements.

Some implementations or embodiments may achieve fewer than all of theforegoing objects.

2. Features of the Disclosure

All ranges of numerical parameters set forth in this disclosure are tobe understood to encompass any and all subranges or “intermediategeneralizations” subsumed herein. For example, a stated range of “1.0 to2.0 eV” for a band gap value should be considered to include any and allsubranges beginning with a minimum value of 1.0 eV or more and endingwith a maximum value of 2.0 eV or less, e.g., 1.0 to 2.0, or 1.3 to 1.4,or 1.5 to 1.9 eV.

Briefly, and in general terms, the present disclosure provides a solarcell assembly comprising:

(a) a multijunction semiconductor solar cell including:

a top or light receiving surface;

a first edge;

a second edge parallel to and opposite the first edge;

a third edge orthogonal to the first edge, and a fourth edge parallel toand opposite the third edge and orthogonal to the first edge;

a fifth edge adjacent to the first edge and having a length shorter thanthe first edge;

a sixth edge adjacent to the fifth edge and the third edge and having alength shorter than the fifth edge;

a seventh edge adjacent to the second edge and having a length shorterthan the second edge;

an eighth edge adjacent to the seventh edge and the third edge andhaving a length shorter than the seventh edge;

a ninth edge adjacent to the second edge and having a length shorterthan the second edge;

a tenth edge adjacent to the ninth edge and the fourth edge and having alength shorter than the ninth edge;

an eleventh edge adjacent to the first edge and having a length shorterthan the first edge;

a twelfth edge adjacent to the eleventh edge and the fourth edge andhaving a length shorter than the eleventh edge; and

a bottom or back surface, opposite to the top surface, including anelectrical contact of a first polarity type;

(b) a first stand-off component having a first edge that is collinearwith the fifth edge of the solar cell, a second edge that is collinearwith the third edge of the solar cell, and a third edge that is parallelto and spaced apart from the sixth edge of the solar cell;

(c) a second stand-off component having a first edge that is collinearwith the ninth edge of the solar cell, a second edge that is collinearwith the fourth edge of the solar cell, and a third edge that isparallel to and spaced apart from the tenth edge of the solar cell; and

(d) a coverglass disposed over the solar cell and the first and secondstand-off components and attached thereto by an adhesive.

In some embodiments, there further comprises a third stand-off componenthaving a first edge that is collinear with the eleventh edge of thesolar cell, a second edge that is collinear with the fourth edge of thesolar cell, and a third edge that is parallel to and spaced apart fromthe twelfth edge of the solar cell.

In some embodiments, there further comprises a bypass diode having afirst edge that is collinear with the seventh edge of the solar cell, asecond edge that is collinear with the third edge of the solar cell, anda third edge that is parallel to and spaced apart from the eighth edgeof the solar cell, the bypass diode being electrically connected inparallel with the solar cell.

In some embodiments, there further comprises a plurality of grid linesextending over the top surface of the solar cell; a first bus barconductively connected to a first set of said grid lines and having afirst portion extending substantially parallel to and proximate to thethird edge of the solar cell, and a second portion extendingsubstantially parallel to and proximate to the sixth edge of the solarcell; and an electrical interconnect coupling the second portion of thefirst bus bar with the top surface of the first stand-off component.

In some embodiments, there further comprises a second bus barconductively connected to a second set of said grid lines and having afirst portion extending substantially parallel to and proximate to thefourth edge of the solar cell, and a second portion extendingsubstantially parallel to and proximate to the tenth edge of the solarcell; and an electrical interconnect coupling the second portion of thesecond bus bar with the top surface of the second stand-off component.

In some embodiments, the first and second stand-off components are eachshaped as a triangular prism and each extends from the top surface ofthe solar cell to the bottom surface of the solar cell and forms a firstand second respective electrical contacts of a second polarity type onthe bottom of the assembly.

In some embodiments, the stand-off components are composed of a highlydoped semiconductor material.

In some embodiments, the stand-off components are composed of galliumarsenide.

In some embodiments, the grid lines are arranged parallel to one anotherand substantially orthogonal to the first and second bus bars.

In some embodiments, there is no bus bar along the first and secondedges of the solar cell.

In some embodiments, the stand-off component is a discrete semiconductorelement shaped as a triangular prism having a side length from 2 to 25mm and a height from 120 to 150 microns.

In some embodiments, the stand-off components are disposed in oppositecorners of the solar cell.

In some embodiments, there further comprises a bypass diode disposedadjacent to one of the corners of the solar cell.

In some embodiments, the bypass diode is triangular in shape having afirst external edge that is collinear with one of the four long edges ofthe solar cell and a second external edge that is collinear with theedge of one of the cropped corners of the cell.

In some embodiments, the discrete semiconductor element has first andsecond end surfaces which are metallized with a metal to a thickness ofapproximately 5 microns to form a contact or bonding pad.

In some embodiments, the first, second, third and fourth edges are allof equal length, and the fifth, sixth, and ninth edges are all of equallength and smaller than that of the first edge.

In some embodiments, the eighth edge is a different length than thefifth edge, but smaller than the first edge.

In some embodiments, the first set of grid lines are electricallyseparate from the second set of grid lines.

In another aspect, the present disclosure provides a back contact solarcell assembly comprising:

(a) a multijunction semiconductor solar cell including: a top or lightreceiving surface; a plurality of grid lines extending over the topsurface of the solar cell; a bottom or back surface, opposite to the topsurface, including an electrical contact of a first polarity; a firstbus bar conductively connected to a first set of said grid lines andhaving a first portion extending substantially parallel to and proximatea first edge of the solar cell, and a second portion extendingsubstantially parallel to and proximate to a second edge of the solarcell adjacent to the first edge; a second bus bar spaced apart anddistinct from the first bus bar and conductively connected to a secondset of grid lines and having a first portion extending substantiallyparallel to and proximate to a third edge of the solar cell, and asecond portion extending substantially parallel to and proximate afourth edge of the solar cell adjacent to the third edge; wherein thethird and fourth edges are disposed on the opposite side of the solarcell from the first and second edges;

(b) a first discrete conductive stand-off component spaced apart fromthe solar cell and proximate to the first bus bar and electricallycoupled thereto, the first stand-off component extending from the topsurface of the solar cell to the bottom surface of the solar cell toform a first electrical contact of a second polarity type on the bottomof the assembly;

(c) a second discrete conductive stand-off component spaced apart fromthe solar cell and proximate to the second bus bas and electricallycoupled thereto, the second stand-off component extending from the topsurface of the solar cell to the bottom surface of the solar cell toform a second electrical contact of a second polarity type on the bottomof the assembly; and

(d) a coverglass disposed over the solar cell and the first and secondstand-off components and attached thereto by an adhesive.

In another aspect, the present disclosure provides a solar cell arraycomprising: a substrate; a plurality of conductive traces including afirst conductive trace and a second conductive trace, each of theconductive traces being supported by the substrate; a plurality of solarcells including a first solar cell and a second solar cell, each solarcell comprising a top surface with a top contact of a first polarity anda back surface with a first back contact electrically coupled to the topcontact by at least a first discrete semiconductor interconnect element,and a second back contact coupled to the back surface of the solar cellforming a contact of a second polarity; wherein the first solar cell isarranged on the substrate with its first back contact bonded to a firstend portion of the conductive trace, and wherein the second solar cellis arranged on the substrate with its second back contact bonded to asecond end portion of the first conductive trace.

In another aspect, the present disclosure provides a solar cell assemblycomprising: a support comprising a first side and an opposing secondside; a conductive layer comprising first and second spaced-apartconductive portions disposed on the first side of the support; aplurality of solar cell assemblies mounted on the first side of thesupport, each solar cell of the plurality of solar cell assemblycomprising a top surface including a contact of a first polarity type,and a rear surface including a contact of a second polarity type; aconductive element in the solar cell assembly extending from the topsurface of the assembly to the rear surface of the assembly, eachrespective conductive element making electrical contact with the contactof the first polarity type of a respective solar cell and extendingalong a cut out in the side of the solar cell to make electrical contactwith the first conductive portion disposed on the first side of thesupport, and the contact of second polarity of the solar cell makingelectrical contact with the second conductive portion of the conductivelayer.

In another aspect, the present disclosure provides a solar cell withgrid lines disposed along the top surface thereof, a first bus barconnected to a first end portion of the grid lines, a second bus barconnected to a second end portion of the grid lines opposite to thefirst end portion, a first discrete semiconductor element connected tothe first bus bar, and a second discrete semiconductor element connectedto the second bus bar.

In some embodiments, the conductive traces are metal traces having athickness in the range of from 1 μm and up to 50 μm, the substratecomprises a polyimide film, and the solar cells are III-V compoundsemiconductor solar cells having cropped corners.

In another aspect, the present disclosure provides a method of producinga solar cell assembly, including providing a flexible substrate;providing a plurality of conductive traces on the substrate, theplurality of conductive traces including a first conductive trace and asecond conductive trace, each of the conductive traces being at leastpartly adhered to the substrate, each of the conductive tracescomprising a first end portion and a second end portion; providing aplurality of solar cells including a first solar cell and a second solarcell, each solar cell comprising a top surface with a top contact of afirst polarity and a back surface with a back contact of a secondpolarity; and bonding the back contact of the first solar cell to thefirst end portion of the first conductive trace, bonding the backcontact of the second solar cell to the first end portion of the secondconductive trace, and bonding the second end portion of the firstconductive trace to the top contact of the second solar cell forconnecting the first solar cell and the second solar cell in electricalseries.

According to an aspect of the present disclosure, there is provided amethod of fabricating a solar cell array by assembling a solar cellassembly to a support. The method includes disposing discrete spacedapart metallized traces on the upper surface of the support; dispensinga conductive adhesive on the support or on the discrete contacts on theback of the solar cell assembly or on the traces on the support; andlaying down the solar cell assembly on the support so that the bondingpads of opposite polarity on the back of the solar cell assembly areelectrically coupled to respective trace lines on the support. Thesupport may be a flexible polyimide film or a rigid panel.

One aspect of the disclosure relates to a method of producing a solarcell assembly, comprising:

providing a flexible substrate;

providing a plurality of conductive traces on the substrate, theplurality of conductive traces including a first conductive trace and asecond conductive trace, each of the conductive traces being at leastpartly adhered to the substrate, each of the conductive tracescomprising a first end portion and a second end portion;

providing a solar cell comprising a top surface with a top contact of afirst polarity and a back surface with a back contact of a secondpolarity;

bonding the back contact of the first solar cell to the first endportion of the first conductive trace;

bonding the back contact of the second solar cell to the first endportion of the second conductive trace; and

bonding the second end portion of the first conductive trace to the topcontact of the second solar cell for connecting the first solar cell andthe second solar cell in electrical series.

In the present context, the term “trace” refers to a conductive layer onthe substrate, preferably a thin conductive layer, for example, aconductive layer having a thickness in the range of from 1 μm and up to50 μm. The traces can be of a conductive material, such as of metal, forexample, copper, gold, silver, nickel, or other materials and conductivealloys thereof.

Although reference has been made to a first solar cell and a secondsolar cell in series, more generally, any number of solar cells may beconnected in series, for example, N solar cells on a panel can all beconnected in series by bonding the second end portion of thecorresponding (N−1) conductive traces to the top contact of thesubsequent or preceding solar cell.

In another aspect, the bonding between the solar cell contacts and thefirst and second end portions of the traces can take place by anysuitable means, including welding (such as laser welding), by using aconductive adhesive, soldering, or ultrasonic bonding.

A flexible and insulating substrate thus supports a plurality ofseparate conductive traces. In some embodiments, the conductive layer isa metal layer such as a copper layer, having a thickness in the range offrom 1 μm and up to 50 μm. In some embodiments, the step of providingthe conductive layer on the substrate comprises attaching the conductivelayer to the substrate in an adhesive-less manner, to limit outgassingwhen the assembly is used in a space environment. Any method suitablefor selectively removing part of the conductive layer can be used toestablish the traces as defined above.

The back and/or top contacts of the solar cells can in some embodimentsbe bonded to the respective portions of the conductive traces using abonding agent such as conductive bonding material, for example, a metalalloy, such as an indium alloy, such as an indium lead alloy. Indiumlead has appropriate heat conduction characteristics and at the sametime, indium is advantageous as it provides for ductility, therebyreducing the risk for cracks in the bonds between the solar cells andthe conductive traces when the assembly is subjected to bending forces.

Another aspect of the disclosure relates to a solar cell assembly,comprising:

a plurality of solar cells including a first solar cell and a secondsolar cell, each solar cell comprising a top surface with a top contactof a first polarity and a back surface with a back contact of a secondpolarity;

a flexible substrate;

a plurality of conductive traces including a first conductive trace anda second conductive trace, each of the conductive traces being at leastpartly adhered to the flexible substrate;

wherein the first solar cell is arranged on the substrate with its backcontact bonded to a first end portion of the first conductive trace, andwherein the second solar cell is arranged on the substrate with its backcontact bonded to a first end portion of the second conductive trace;

wherein the first conductive trace comprises a second end portion bondedto the top contact of the second solar cell for connecting the firstsolar cell and the second solar cell in electrical series.

In some embodiments, the solar cells are III-V compound semiconductorsolar cells.

In some embodiments, the method further comprises welding the backsurfaces of the second end portions to the top contacts of therespective solar cells.

Additional aspects, advantages, and novel features of the presentinvention will become apparent to those skilled in the art from thisdisclosure, including the following detailed description as well as bypractice of the invention. While the invention is described below withreference to illustrative embodiments, it should be understood that theinvention is not limited thereto. Those of ordinary skill in the arthaving access to the teachings herein will recognize additionalapplications, modifications and embodiments in other fields, which arewithin the scope of the invention as disclosed and claimed herein andwith respect to which the invention could be of utility.

“Top surface” is used herein to refer to a surface that would facetowards incoming solar radiation in normal operation of the flexiblesolar array, but need not refer to a surface that is directly exposed tothe solar radiation, such as a top surface of a backing layer. “Backsurface” is used to refer to a surface that would face away fromincoming solar radiation in normal operation. “Upwards” is used hereinto indicate a direction relative to these top and bottom surfaces. Asurface abutting another surface need not abut across the entirety ofboth surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

To complete the description and in order to provide for a betterunderstanding of the disclosure, a set of drawings is provided. Saiddrawings form an integral part of the description and illustrateembodiments of the disclosure, which should not be interpreted asrestricting the scope of the disclosure, but just as examples of how thedisclosure can be carried out. The drawings comprise the followingfigures:

FIG. 1 is a top plan view of a semiconductor wafer with a solar cellwith cropped corners disposed therein, with edge lines depicting how thesolar cell would be scribed or cut from the semiconductor wafer;

FIG. 2A is a top schematic view of a portion of a solar cell arrayshowing the interconnection of two adjacent solar cells according to theprior art;

FIG. 2B is a cross sectional view of the solar cell array through the2B-2B plane shown in FIG. 2A;

FIG. 3A is a highly simplified top plan view of a portion of a solarcell assembly depicting a plurality of stand-off elements adjacent tothe solar cell in a first embodiment;

FIG. 3B is a highly simplified top plan view of a portion of a solarcell assembly depicting a plurality of stand-off elements adjacent tothe solar cell in a second embodiment;

FIG. 3C is a top plan view of a portion of a solar cell of FIG. 3Bdepicting the grid lines, bus bars, and contact pads according to thepresent disclosure;

FIG. 3D is a bottom plan view of the solar cell of FIG. 3B with aninterconnect to the bypass diode;

FIG. 4A is a top plan view of a solar cell module with an array of solarcells according to the present disclosure;

FIG. 4B is a bottom plan view of the module of FIG. 4A;

FIG. 5A is a highly simplified cross-sectional view of a portion of asolar cell;

FIG. 5B is a cross-sectional view of the solar cell of FIG. 5A with anadjacent stand-off element;

FIG. 5C is a cross-sectional view of the solar cell of FIG. 5A with aninterconnect to the stand-off element shown through the 5C-5C plane inFIG. 4A;

FIG. 6 is a top plan view of the portion of the solar cell and thestand-off element as shown in FIG. 5C with an interconnect elementconnecting the solar cell and the stand-off element; and

FIG. 7 is a schematic diagram of an array of four solar cells of FIGS.4A and 4B with all of the solar cells connected in series.

DETAILED DESCRIPTION

Details of the present disclosure will now be described includingexemplary aspects and embodiments thereof. Referring to the drawings andthe following description, like reference numbers are used to identifylike or functionally similar elements, and are intended to illustratemajor features of exemplary embodiments in a highly simplifieddiagrammatic manner. Moreover, the drawings are not intended to depictevery feature of the actual embodiment nor the relative dimensions ofthe depicted elements, and are not drawn to scale.

It is known in the art to arrange a solar cell array on a panel byconnecting the solar cells in a series circuit by connecting the topcontact (of a first polarity or conductivity type) of one solar cell tothe back contact (of a second polarity or conductivity type) of thepreceding or following adjacent solar cell. This connection can forexample be carried out by bonding a conductive element (or“interconnect”) to the top contact of a first solar cell and to the backcontact of the other solar cell, or to a conductive trace to which theback contact is connected. US-2010/0282288-A1 shows one example of thiskind of arrangement. However, this involves the use of additionalconductive elements, such as for example conductive wires, and often theuse of additional bonds between components.

By using a discrete conductive semiconductor element (in one embodiment)according to the present disclosure bonded to the top contact of onesolar cell and bonding this element to an adjacent solar cell in theseries of solar cells there is no need for additional components toestablish the connection in series of the solar cells, and the number ofbonding points can be minimized. This can be advantageous from the pointof view of, for example, ease of manufacture, weight of the assembly,cost and/or reliability.

For CIC building a one-cell-per-wafer cell provides significant costbenefit compared to the two-cells-per-wafer solution by reducing thepiece part count by half. But this benefit comes with a cost—The cellperformance can reduce by 2% relative on efficiency due to the increasedseries resistance as the grid fingers are twice as long and only one busbar is practically applicable for the one-cell-per-wafer cellconfiguration when current stringing technique is applied.

For this invention an all-bottom contact CIC is created by integratingtwo or more pieces of electrically conductive standoffs into the CIC.The top contact of the cell, along with the top contact of the bypassdiode, can be electrically connected to the top side of the standoff bymeans of interconnect welding, ribbon bonding or other methods. Same asthe cell and bypass diode the standoffs are also structurally attachedto the coverglass by optically transparent adhesives. By having two ormore standoffs, the current collecting is now from both sides of thecell which can significantly reduce the I²R loss from the seriesresistance with the help of a two bus bar cell configuration. Byelectrically connecting all the bottom contacts of the standoffs bymeans such as flexible circuits, the efficiency of theone-sell-per-wafer cell can be recovered to the same level of atwo-sells-per-wafer cell.

In addition to that, an approximately 0.2% extra current generation, forthe case of a 65 cm² one-cell-per-wafer cell, may be achieved byreplacing the 1.4×2.8 mm welding pads with 0.25×0.5 mm bonding pads,with two bonding pads in each opposite cropped corner. Although theFigures depict two bonding pads for each cropped corner for increasedreliability, in some embodiments only one bonding pad may be used ineach corner, although the interconnect may make electrical contact tothe single bonding pad with two discrete connectors and bondinglocations on the bonding pad.

FIG. 1 is a top plan view of a semiconductor wafer 100 with a solar cell101 with cropped corners 102, 103, 104, and 105 disposed therein, withedge lines depicting how the solar cell 100 would be scribed or cut fromthe semiconductor wafer 100.

FIG. 2A is a top schematic view of a portion of a solar cell arrayshowing the interconnection of two adjacent solar cells 100 and 106according to the prior art. Each solar cell has contact pads 110, 111and 112 along one edge thereof. The interconnect 200 has two armsconnected to contact pads 111 and 112 respectively of solar cell 106,and is positioned in the space 210 between the solar cells.

FIG. 2B is a cross sectional view of a portion of the solar cell arraythrough the 2B-2B plane shown in FIG. 2A. The interconnect 200 has onearm 201 connected to the top contact pad 111 of solar cell 101, and aportion 203 connected to the back contact 121 of solar cell 106. A coverglass 150 is disposed over solar cell 101 and a cover glass 151 isdisposed over solar cell 106.

FIG. 3A is a highly simplified top plan view of a portion of a solarcell assembly depicting a plurality of stand-off elements adjacent tothe solar cell in a first embodiment.

In the first cropped corner 102 is a first stand-off element 320, in thesecond cropped corner 103 is a second stand-off element 321, in thethird cropped corner 104 is a third stand-off element 322, and in thefourth cropped corner 105 is a fourth stand-off element 323. Moreover,in the third cropped corner is a bypass diode 330.

FIG. 3B is a highly simplified bottom plan view of a portion of a solarcell assembly depicting a plurality of stand-off elements adjacent tothe solar cell in a second embodiment.

In particular, the figure depicts a multijunction semiconductor solarcell including: a first edge 402; a second edge 416 parallel to andopposite the first edge; a third edge 420 orthogonal to the first edge,and a fourth edge 412 parallel to and opposite the third edge andorthogonal to the first edge; a fifth edge 422 adjacent to the firstedge and having a length shorter than the first edge; a sixth edge 421adjacent to the fifth edge 422 and the third edge and having a lengthshorter than the fifth edge 422; a seventh edge 417 adjacent to thesecond edge and having a length shorter than the second edge 416; aneighth edge 419 adjacent to the seventh edge 417 and the third edge andhaving a length equal to or shorter than the seventh edge 417; a ninthedge 415 adjacent to the second edge 416 and having a length shorterthan the second edge 416; a tenth edge 413 adjacent to the ninth edge415 and the fourth edge 412 and having a length equal to or shorter thanthe ninth edge 415; an eleventh edge 410 adjacent to the first edge 402and having a length shorter than the first edge 402; a twelfth edge 411adjacent to the eleventh edge 410 and the fourth edge and having alength equal to or shorter than the eleventh edge 410.

The Figure further depicts: (a) a first stand-off component 343 having afirst edge 433 that is collinear with the second edge 416 of the solarcell, a second edge 418 that is collinear with the eighth edge 419 ofthe solar cell, and a third edge 432 that is parallel to and spacedapart from the seventh edge of the solar cell; (b) a second stand-offcomponent 342 having a first edge 403 that is collinear with the firstedge 402 of the solar cell, a second edge 404 that is collinear with thetwelfth edge of the solar cell, and a third edge 405 that is parallel toand spaced apart from the eleventh edge of the solar cell; and (c) athird stand-off component 341 having a first edge 423 that is collinearwith the second edge 416 of the solar cell, a second edge 414 that iscollinear with the tenth edge of the solar cell, and a third edge 424that is parallel to and spaced apart from the ninth edge of the solarcell. (d) a coverglass disposed over the solar cell and the first andsecond stand-off components 343 and 342 and attached thereto by anadhesive.

The solar cell assembly in FIG. 3B further depicts a bypass diode 340having a first edge 401 that is collinear with the first edge of thesolar cell, a second edge 430 that is collinear with the sixth edge ofthe solar cell, and a third edge 431 that is parallel to and spacedapart from the fifth edge of the solar cell, the bypass diode beingelectrically connected in parallel with the solar cell.

FIG. 3C is a top plan view of a portion of a solar cell of FIG. 3Bdepicting the grid lines, bus bars, and contact pads according to thepresent disclosure.

In particular, there is illustrated a plurality of grid lines 460extending over the top surface of the solar cell 101; a first bus bar450 conductively connected to a first set of said grid lines 460 andhaving a first portion extending substantially parallel to and proximateto the first edge 402 of the solar cell, and a second portion extendingsubstantially parallel to and proximate to the fifth edge of the solarcell; and electrical interconnects 458, 459 coupling the second portionof the first bus bar 450 with contact pads 452 and 455 with the topsurface of the bypass diode 340.

In some embodiments, there further comprises a second bus bar 451conductively connected to a second set of grid lines (which may or maynot be identical with, or electrically connected to the first set ofgrid lines 460) and having a first portion extending substantiallyparallel to and proximate to the second edge of the solar cell 101, anda second portion extending substantially parallel to and proximate tothe ninth edge of the solar cell; and electrical interconnects 454, 455coupling the second portion of the second bus bar 451 with contact pads456 and 457 with the top surface of a first stand-off component 341.

In some embodiments, there is a second stand-off component 342, and insome embodiments a third stand-off component 343, so that one stand-offcomponent is disposed in each cropped corner of the solar cell 101.

In some embodiments, the stand-off components are each shaped as atriangular prism and each extends from the top surface of the solar cell101 to the bottom surface of the solar cell 101 and forms a first andsecond respective electrical contacts of a second polarity type on thebottom of the assembly.

In some embodiments, the stand-off components 341, 342, 343 are composedof a highly doped semiconductor material.

In some embodiments, the stand-off components 341, 342, 343 are composedof gallium arsenide.

In some embodiments, the grid lines 460 are arranged parallel to oneanother and substantially orthogonal to the first and second bus bars450 and 451 respectively.

In some embodiments, there is no bus bar along the first, third andfourth edges 402, 420 and 412 respectively of the solar cell.

In some embodiments, the stand-off component 341, 342, 343 is a discretesemiconductor element shaped as a triangular prism having a side lengthfrom 2 to 25 mm and a height from 120 to 150 microns.

In some embodiments, the stand-off element components 343 and 342 aredisposed in opposite corners of the solar cell.

In some embodiments, there further comprises a bypass diode 340 disposedadjacent to one of the corners of the solar cell.

In some embodiments, the bypass diode 340 is triangular in shape havinga first external edge 401 that is collinear with one 402 of the fourlong edges of the solar cell and a second external edge 461 that iscollinear with the edge 421 of one of the cropped corners of the solarcell.

FIG. 3D is a bottom plan view of the solar cell of FIG. 3B depicting theinterconnect 461 to the bottom surface 460 of the bypass diode 340,which provides an electrical connection to the contact pad 462 on thebackside of the solar cell 101. Thus, the bypass diode 340 iselectrically in parallel with the subcells of the solar cell 101.

FIG. 4A is a top plan view of a solar cell module 190 with an array offour solar cells according to the present disclosure.

The Figure depicts solar cells 130, 140, 160 and 170, bypass diode 131,141, 161 and 171 disposed in the upper left cropped corner region of thesolar cells 130, 140, 160 and 170 respectively. Also depicted arestandoff components 132, 133 and 134 disposed in cropped off corners ofsolar cell 130, standoff components 142, 143, and 144 disposed incropped off corners of solar cell 140; standoff components 162, 163 and164 disposed in cropped off corners of solar cell 160; and standoffcomponents 172, 173 and 174 disposed in cropped off corners of solarcell 170.

Also depicted is a first interconnect element 136 making an electricalconnection between a first bus bar (not shown) on the top surface ofsolar cell 130 with the top surface of standoff component 132 and asecond interconnect element 135 making an electrical connection betweena second bus bar (not shown) on the top surface of solar cell 130 withthe top surface of standoff component 134.

Also depicted is a first interconnect element 146 making an electricalconnection between a first bus bar (not shown) on the top surface ofsolar cell 140 with the top surface of standoff component 142 and asecond interconnect element 145 making an electrical connection betweena second bus bar (not shown) on the top surface of solar cell 140 withthe top surface of standoff component 144.

Also depicted is a first interconnect element 166 making an electricalconnection between a first bus bar (not shown) on the top surface ofsolar cell 160 with the top surface of standoff component 162 and asecond interconnect element 165 making an electrical connection betweena second bus bar (not shown) on the top surface of solar cell 160 withthe top surface of standoff component 164.

Also depicted is a first interconnect element 176 making an electricalconnection between a first bus bar (not shown) on the top surface ofsolar cell 170 with the top surface of standoff component 172 and asecond interconnect element 175 making an electrical connection betweena second bus bar (not shown) on the top surface of solar cell 170 withthe top surface of standoff component 174.

FIG. 4B is a bottom plan view of the module of FIG. 4A.

In particular, the Figure depicts an interconnect 139, 149, 169 and 179from the back surface of the bypass diode 131, 141, 161 and 171respectively to the backside surface pad of the solar cell 130, 140, 160and 170 respectively. Thus, the bypass diodes 131, 141, 161 and 171 areconnected in parallel with the subcells of the solar cells 130, 140, 160and 170 respectively.

In the embodiment depicted in FIG. 4B, the solar cells 130, 140, 160 and170 are connected in an electrical series circuit by means ofinterconnects 138, 148 and 168.

More particularly, interconnect 138 connects the bottom surface of thestandoff component 142 with a pad 139 on the back surface of solar cell130. Since standoff component 142 is connected with the n-terminal ofsolar cell 140 (see FIG. 4A, and in particular through interconnect146), a p to n series connection is made between solar cells 130 and140.

Similarly, interconnect 148 connects the bottom surface of standoffcomponent 163 with a pad 151 on the back surface of solar cell 140.Since standoff component 163 is connected with the n-terminal of solarcell 160 (see FIG. 4A, and in particular through interconnect 152), a pto n series connection is made between solar cells 140 and 160.

Similarly, interconnect 168 connects the bottom surface of standoffcomponent 174 with a pad 153 on the back surface of solar cell 160.Since standoff component 174 is connected with the n-terminal of solarcell 170 (see FIG. 4A, and in particular through interconnect 175), a pto n series connection is made between solar cells 160 and 170.

An n-terminal 181 is connected by a link 180 to stand-off component 132of solar cell 130, thereby forming one end of the serial connection. Ap-terminal 183 is connected by a link 182 to pad 179 on the backside ofsolar cell 170, thereby forming the other end of the serial connection.

FIG. 5A is a highly simplified cross-sectional view of a portion of asolar cell 500 depicting the top and bottom contacts.

More particularly, the solar cell 500 includes a semiconductor substrate501, various epitaxial layers 502 deposited over the substrate 501forming one or more subcells, a window layer 503 disposed over the topsubcell, and a semiconductor contact layer 504 disposed over the windowlayer. A metal layer 505 is disposed over the contact layer 504 to allowan electrical contact to be made to the top side of the solar cell 500.An Antireflective (ARC) dielectric coating layer 506 is then depositedover the top surface of the solar cell 500.

FIG. 5B is a cross-sectional view of the solar cell of FIG. 5A with anadjacent stand-off element 510 (herein shown in cross-section in oneembodiment as composed of metal) disposed adjacent the edge of the solarcell.

FIG. 5C is a cross-sectional view of the solar cell of FIG. 5A with aninterconnect element 511 to the stand-off element 510 shown through the5C-5C plane in FIG. 4A, thereby making a contact surface 513 on thebottom of the stand-off element 510 available on the back side of thesolar cell assembly to provide electrical connection to the metal layer505 on the top side of the solar cell.

FIG. 6 is a top plan view of the portion of the solar cell and thestand-off element 510 as shown in FIG. 5C with an interconnect element511 connecting the metal layer 505 of the solar cell and the stand-offelement 511. The interconnect element 511 is substantially planar with aserpentine shape so as to provide stress relief that may be occasionedby the separate movement of the solar cell and the stand-off element511.

FIG. 7 is a schematic diagram of an array of four solar cells 130, 140,160 and 170 of FIGS. 4A and 4B with all of the solar cells connected inseries between the N terminal 181 and the P terminal 183.

In some embodiments of the disclosure, the solar cells can be of thetype described in U.S. patent application Ser. No. 12/218,582 filed Jul.18, 2008, hereby incorporated by reference.

Thus, while the description of the semiconductor device described in thepresent disclosure has focused primarily on solar cells or photovoltaicdevices, persons skilled in the art know that other optoelectronicdevices, such as thermophotovoltaic (TPV) cells, photodetectors andlight-emitting diodes (LEDS), are very similar in structure, physics,and materials to photovoltaic devices with some minor variations indoping and the minority carrier lifetime. For example, photodetectorscan be the same materials and structures as the photovoltaic devicesdescribed above, but perhaps more lightly-doped for sensitivity ratherthan power production. On the other hand LEDs can also be made withsimilar structures and materials, but perhaps more heavily-doped toshorten recombination time, thus radiative lifetime to produce lightinstead of power. Therefore, this invention also applies tophotodetectors and LEDs with structures, compositions of matter,articles of manufacture, and improvements as described above forphotovoltaic cells.

Without further analysis, from the foregoing others can, by applyingcurrent knowledge, readily adapt the present invention for variousapplications. Such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

The invention claimed is:
 1. A solar cell assembly comprising: (a) amultijunction semiconductor solar cell including: a top or lightreceiving surface; a first edge; a second edge parallel to and oppositethe first edge; a third edge orthogonal to the first edge, and a fourthedge parallel to and opposite the third edge and orthogonal to the firstedge; a fifth edge adjacent to the first edge and having a lengthshorter than the first edge; a sixth edge adjacent to the fifth edge andthe third edge and having a length shorter than the fifth edge; aseventh edge adjacent to the second edge and having a length shorterthan the second edge; an eighth edge adjacent to the seventh edge andthe third edge and having a length shorter than the seventh edge; aninth edge adjacent to the second edge and having a length shorter thanthe second edge; a tenth edge adjacent to the ninth edge and the fourthedge and having a length shorter than the ninth edge; an eleventh edgeadjacent to the first edge and having a length shorter than the firstedge; a twelfth edge adjacent to the eleventh edge and the fourth edgeand having a length shorter than the eleventh edge; and a bottom or backsurface, opposite to the top surface, including an electrical contact ofa first polarity type, wherein a bounding rectangle is defined by linesalong the first edge, the second edge, the third edge and the fourthedge; (b) a first stand-off component having a first edge that iscollinear with the fifth edge of the solar cell, a second edge that iscollinear with the third edge of the solar cell, and a third edge thatis parallel to and spaced apart from the sixth edge of the solar cell;(c) a second stand-off component having a first edge that is collinearwith the ninth edge of the solar cell, a second edge that is collinearwith the fourth edge of the solar cell, and a third edge that isparallel to and spaced apart from the tenth edge of the solar cell; and(d) a coverglass disposed over the solar cell and the first and secondstand-off components and attached thereto by an adhesive, wherein thefirst stand-off component and the second stand-off component are withinthe bounding rectangle.
 2. A solar cell assembly as defined in claim 1,further comprising: a third stand-off component having a first edge thatis collinear with the eleventh edge of the solar cell, a second edgethat is collinear with the fourth edge of the solar cell, and a thirdedge that is parallel to and spaced apart from the twelfth edge of thesolar cell.
 3. A solar cell assembly as defined in claim 1, furthercomprising a bypass diode having a first edge that is collinear with theseventh edge of the solar cell, a second edge that is collinear with thethird edge of the solar cell, and a third edge that is parallel to andspaced apart from the eighth edge of the solar cell, the bypass diodebeing electrically connected in parallel with the solar cell.
 4. A solarcell assembly as defined in claim 1, further comprising a plurality ofgrid lines extending over the top surface of the solar cell; a first busbar conductively connected to a first set of said grid lines and havinga first portion extending substantially parallel to and proximate to thethird edge of the solar cell, and a second portion extendingsubstantially parallel to and proximate to the sixth edge of the solarcell; and an electrical interconnect coupling the second portion of thefirst bus bar with the top surface of the first stand-off component. 5.A solar cell assembly as defined in claim 4, further comprising: asecond bus bar conductively connected to a second set of said grid linesand having a first portion extending substantially parallel to andproximate to the fourth edge of the solar cell, and a second portionextending substantially parallel to and proximate to the tenth edge ofthe solar cell; and an electrical interconnect coupling the secondportion of the second bus bar with the top surface of the secondstand-off component.
 6. A solar cell assembly as defined in claim 1,wherein the first and second stand-off components are each shaped as atriangular prism and each extends from the top surface of the solar cellto the bottom surface of the solar cell and forms a first and secondrespective electrical contacts of a second polarity type on the bottomof the assembly.
 7. A solar cell assembly as defined in claim 1, whereinthe stand-off components are composed of a highly doped semiconductormaterial.
 8. A solar cell assembly as defined in claim 7, wherein thestand-off components are composed of gallium arsenide.
 9. A solar cellassembly as defined in claim 1, wherein the grid lines are arrangedparallel to one another and substantially orthogonal to the first andsecond bus bars.
 10. A solar cell assembly as defined in claim 1,wherein there is no bus bar along the first and second edges of thesolar cell.
 11. A solar cell assembly as defined in claim 6, wherein thestand-off component is a discrete semiconductor element shaped as atriangular prism having a side length from 2 to 25 mm and a height from120 to 150 microns.
 12. A solar cell assembly as defined in claim 5,wherein the stand-off components are disposed in opposite corners of thesolar cell.
 13. A solar cell as defined in claim 1, further comprising abypass diode disposed adjacent to one of the corners of the solar cell.14. A solar cell assembly as defined in claim 13, wherein the bypassdiode is triangular in shape having a first external edge that iscollinear with one of the four long edges of the solar cell and a secondexternal edge that is collinear with the edge of one of the croppedcorners of the cell.
 15. A solar cell assembly as defined in claim 11,wherein the discrete semiconductor element has first and second endsurfaces which are metallized with a metal to a thickness ofapproximately 5 microns to form a contact or bonding pad.
 16. A solarcell assembly as defined in claim 1, wherein the first, second, thirdand fourth edges are all of equal length, and the fifth, sixth, andninth edges are all of equal length and smaller than that of the firstedge.
 17. A solar cell assembly as defined in claim 3, wherein theeighth edge is a different length than the fifth edge, but smaller thanthe first edge.
 18. A solar cell assembly as defined in claim 5, whereinthe first set of grid lines are electrically separate from the secondset of grid lines.
 19. A solar cell assembly comprising: (a) amultijunction semiconductor solar cell including: a top or lightreceiving surface; a first edge; a second edge parallel to and oppositethe first edge; a third edge orthogonal to the first edge, and a fourthedge parallel to and opposite the third edge and orthogonal to the firstedge; a fifth edge adjacent to the first edge and having a lengthshorter than the first edge; a sixth edge adjacent to the fifth edge andthe third edge and having a length shorter than the fifth edge; aseventh edge adjacent to the second edge and having a length shorterthan the second edge; an eighth edge adjacent to the seventh edge andthe third edge and having a length shorter than the seventh edge; aninth edge adjacent to the second edge and having a length shorter thanthe second edge; a tenth edge adjacent to the ninth edge and the fourthedge and having a length shorter than the ninth edge; an eleventh edgeadjacent to the first edge and having a length shorter than the firstedge; a twelfth edge adjacent to the eleventh edge and the fourth edgeand having a length shorter than the eleventh edge; and a bottom or backsurface, opposite to the top surface, including an electrical contact ofa first polarity type, wherein a bounding rectangle is defined by linesalong the first edge, the second edge, the third edge and the fourthedge; (b) a first stand-off component having a first edge that iscollinear with the fifth edge of the solar cell, a second edge that iscollinear with the third edge of the solar cell, and a third edge thatis parallel to and spaced apart from the sixth edge of the solar cell;(c) a second stand-off component having a first edge that is collinearwith the ninth edge of the solar cell, a second edge that is collinearwith the fourth edge of the solar cell, and a third edge that isparallel to and spaced apart from the tenth edge of the solar cell; and(d) a coverglass disposed over the solar cell and the first and secondstand-off components and attached thereto by an adhesive, wherein thefirst and second stand-off components are each a discrete semiconductorelement shaped as a triangular prism having a side length from 2 to 25mm and a height from 120 to 150 microns within the bounding rectangle,and each extends from the top surface of the solar cell to the bottomsurface of the solar cell, the first and second stand-off componentsforming respectively a first electrical contact and a second electricalcontact of a second polarity type on the bottom of the assembly.
 20. Asolar cell assembly comprising: (a) a multijunction semiconductor solarcell including: a top or light receiving surface; a first edge; a secondedge parallel to and opposite the first edge; a third edge orthogonal tothe first edge, and a fourth edge parallel to and opposite the thirdedge and orthogonal to the first edge; a fifth edge adjacent to thefirst edge and having a length shorter than the first edge; a sixth edgeadjacent to the fifth edge and the third edge and having a lengthshorter than the fifth edge; a seventh edge adjacent to the second edgeand having a length shorter than the second edge; an eighth edgeadjacent to the seventh edge and the third edge and having a lengthshorter than the seventh edge; a ninth edge adjacent to the second edgeand having a length shorter than the second edge; a tenth edge adjacentto the ninth edge and the fourth edge and having a length shorter thanthe ninth edge; an eleventh edge adjacent to the first edge and having alength shorter than the first edge; a twelfth edge adjacent to theeleventh edge and the fourth edge and having a length shorter than theeleventh edge; and a bottom or back surface, opposite to the topsurface, including an electrical contact of a first polarity type,wherein the first, second, third and fourth edges are all of equallength, and the fifth, sixth, and ninth edges are all of equal lengthand smaller than that of the first edge and wherein a bounding square isdefined by lines along the first edge, the second edge, the third edgeand the fourth edge; (b) a first stand-off component having a first edgethat is collinear with the fifth edge of the solar cell, a second edgethat is collinear with the third edge of the solar cell, and a thirdedge that is parallel to and spaced apart from the sixth edge of thesolar cell; (c) a second stand-off component having a first edge that iscollinear with the ninth edge of the solar cell, a second edge that iscollinear with the fourth edge of the solar cell, and a third edge thatis parallel to and spaced apart from the tenth edge of the solar cell;(d) a bypass diode having a first edge that is collinear with theseventh edge of the solar cell, a second edge that is collinear with thethird edge of the solar cell, and a third edge that is parallel to andspaced apart from the eighth edge of the solar cell, the bypass diodebeing electrically connected in parallel with the solar cell; and (e) aplurality of grid lines extending over the top surface of the solarcell; (f) a first bus bar conductively connected to a first set of saidgrid lines and having a first portion extending substantially parallelto and proximate to the third edge of the solar cell, and a secondportion extending substantially parallel to and proximate to the sixthedge of the solar cell; (g) an electrical interconnect coupling thesecond portion of the first bus bar with the top surface of the firststand-off component; and (h) a coverglass disposed over the solar celland the first and second stand-off components and the bypass diode andattached thereto by an adhesive, wherein the first stand-off componentand the second stand-off component are composed of gallium arsenide andare each shaped as a triangular prism and each extends from the topsurface of the solar cell to the bottom surface of the solar cell andforms a first and second respective electrical contacts of a secondpolarity type on the bottom of the assembly, and wherein the firststand-off component, the second stand-off component, and the bypassdiode are within the bounding square.